Advancement of IT technology in recent years is supported by advances in miniaturization technology. Among them, mold imprinting is expected as a technique which is able to respond to the demands of mass production and fine miniaturization without using expensive equipment such as a projection exposure apparatus in the fields of photolithography or electron beam lithography.
Mold imprinting (hereinafter, referred to as “mold imprinting” or “imprinting”) is conducted by pressing a mold formed with a convexo-concave fine pattern on its surface against a resin (resist) layer which is curable by electromagnetic radiation such as UV on a substrate of silicon, quartz, or resin to transfer the fine structure, and exposing it to radiation such as UV light to cure the resin layer, and thereby immobilizing the transferred fine structure. The resin layer is used as a molded article, and as it is. Furthermore, after releasing the mold, the transfer film layer is subjected to asking treatment by oxygen plasma, and to etching treatment, so that a silicon semiconductor substrate formed with the fine structure of the pattern can be obtained.
The mold that has been released is used repeatedly. In addition, in order not to damage the fine structure pattern of the transfer layer during the release, and in order to improve (shorten) the industrial production cycle, a high mold releasability of the transfer layer from the mold is required. For improving the mold releasability, in general, a silicone-based mold release agent, a fluorine-based coupling agent or the like is applied to the surface of the mold.
On the other hand, as the original mold block (also referred to as a “mother mold” or a “master mold”), the original mold block made of silicon or quartz is generally used, but it is very expensive. Therefore, a mold made of resin (“resin mold”) in place of silicon or quartz, and a replica made of resin (“resin replica mold”) which is a copy of the quartz mold has been developed.
Herein, the resin replica mold means a replica obtained by pressing the original mold block made of quartz (mother mold) against the resin surface and having a fine structure which is transferred in inverse from the convexoconcave of the mother mold (“mother pattern”). This replica is used as a mold (“resin replica mold”) for transfer onto the other resin surface, thereby a mold having a fine structure of the same convexo-concave pattern as the mother pattern (“resin mold”) can be obtained.
In other words, the relationship is as follows: (a) the original mold block of silicon or quartz (mother pattern) produces the resin replica mold (the inverted convexo-concave pattern structure with respect to the mother pattern), and (b) the resin replica mold (the inverted convexo-concave pattern) produces the resin mold (the same convexo-concave pattern as the mother pattern). Thus obtained resin mold is used as an mold for imprinting to establish the industrial process which is economically advantageous.
In the manufacturing step of the resin replica mold and the resin mold as above, a mold releasability is considered. That is, in order not to damage the fine structure pattern of the transfer layer during release, and in order to improve (shorten) the industrial production cycle, a high mold releasability of the transfer layer from the mold is required. For improving the mold releasability, a method of forming a mold release-promoting layer of a silicone-based mold release agent, a fluorine-based coupling agent or the like on the surface of the mold is conventionally known. It is illustrated below:
(1) JP 2002-270541 A discloses a mold for imprinting having a surface treatment layer containing a silyl chloride compound having a fluorine-containing group.
(2) JP 4,111,997 B discloses a method for imprinting wherein a mold is pressed against a resin coating which silicone oil or a fluorine-containing water-repellent agent permeates.
(3) JP 2009-184275 A discloses a method of interposing a mold release agent between a mold and a resin layer to be imprinted.
(4) JP 2010-045092 A discloses a method of applying a mold release agent onto a resist layer before a mold is pressed.
(5) JP 2010-049745 A discloses a patterned layer on which a release coating made of a fluorine-containing compound is formed.
However, according to these methods of applying a mold release agent or the like to form the release coating, when the mold is used for imprinting, durability of the mold is insufficient, and for mass production of the article to which the pattern is transferred cleaning of the mold and retreatment of the release coating are required depending on degradation of the mold releasability. Further improvements are awaited as an industrial production process.
On the other hand, a method for making the resin molding itself with a superior mold releasability is also proposed. For example,
(5) JP 2010-049745 A discloses a method of using a fluorine-containing resin for the convexo-concave fine patterned layer is disclosed. For example, in Example 5 of this publication, the patterned layer is prepared by using NIF-A-1 (produced from Asahi Glass Co., Ltd.) which is a fluorine-containing resin. In this case, the publication says that because of improvement in the mold releasability, occurrence of defects in the mold is prevented even if the number of imprinting exceeds 5,000 times, so that the time period for replacement of the mold in mass production can be extended. However, such invention results in high cost because the patterned layer is prepared from the expensive fluorine-containing resin only, so that further improvement is awaited.